I've got a couple of Einsteins that are currently mounted on my background stands. I've been watching Craig's List of some used stands and saw some PCB 13' stands for $50 each (http://www.paulcbuff.com/ts13ac.php). I only have 9 ft ceilings and am balking at the extra weight and footprint of the 13' stands. I realize my needs may change in the future and that you can't make a 10' stand longer but can make a 13' stand shorter.
Any input would be appreciated.

I have the 12' Buff stands. Even if not extended fully the stability of the wider base is a plus.

Low ceilings are a limiting factor. As stand are moved back to get out of the way for wider views the lights must be raised to keep the angle of the key light-to-face the same.

Outdoors a subject looking level will wind up with skylight shaded by the brow. The solution is to have them look up, then raise the camera position. That then requires adjustment of the height / angle of the key light. Camera usually winds up about 8' off the ground (bring a ladder on outdoor shoots) with the key light up around 12' to match the downward angle of the skylight.

C-Stands are the most versatile stands you can buy and the ones you'll use the most. That's where I'd start. A C-Stand with a standard arm attached to it. They don't go as high, but most of the time you don't need to anyway. Gradually you can add baby C-stands and maybe a couple of hi-rollers or the Buff stands you're looking at already. You don't need to buy them all at once. Add one or two at a time until you finally get a number you're comfortable with. I own about a dozen C-Stands, two hi-roller and an assortment of "standard" light stands of varying sizes. When I go on location, C-Stands are what I take unless I know I need something bigger. Don't forget to get sand bags or shot bags as well.

OP mentioned his ceilings, so I presume that outdoor/travel may be a lesser priority. I have two Junior rollers - one hi, one lo - and always use them in preference to my alu light stands. I could ride them down the street, literally. In a studio, weight is irrelevent if you can wheel it around! Plus, the solidity and footprint make them untippable even with a big boom lofted. The primary purpose of a C stand is holding modifiers on a grip arm (watch that 20lb limit).